Evaluation of spinal cord compression and hyperintense intramedullary lesions on T2-weighted sequences in patients with cervical spondylotic myelopathy using flexion-extension MRI protocol

Background contextAcquired cervical stenosis is caused by the combination of disc protrusion, facet joint degeneration, hypertrophy of the ligamentum flavum, and osteophyte formation. Although these mechanical factors seem to play an important role in the pathogenesis of myelopathy, the role of dynamic factors has been suggested by many authors. Based on these results, dynamic magnetic resonance imaging (MRI) was proposed to improve diagnostic techniques in patients with cervical myelopathy.PurposeThe purpose of the study was to evaluate the importance of dynamic MRI in the assessment of cervical canal stenosis and to determine the percentage of levels in which cord impingement was only visible in the extension MRI and the percentage of cases in which hyperintense intramedullary lesions (HILs) were identified only on the flexion MRI.Study designThis is a retrospective case series study.Patient samplePatients with spondylotic myelopathy who had dynamic cervical MRI at our department from October 2005 to February 2007 were included.Materials and methodsFifty-one consecutive patients with spondylotic myelopathy had MRI in the neutral, flexion, and extension positions of the cervical spine.Outcome measuresThe following entities were evaluated: canal stenosis (the evaluation of the stenosis was based on the Muhle classification) and the presence or absence of HILs.ResultsTwo hundred fifty-five levels were evaluated in the three positions. At each level, the stages in extension were higher than the stages in neutral and flexion positions (p<.05). From C3 to C6, around 22.5% of Stage 3 levels in the extension were Stage 1 in the neutral position. In flexion, HILs are better identified than in neutral and extension positions (p<.05). In 10% of the patients, HILs were identified only in the flexion T2-weighted sequence.ConclusionsExtension MRI helps to identify significant cervical canal stenosis that is partially or completely absent on neutral and flexion MRI and to determine the exact number of levels to decompress surgically. Flexion MRI permits better visualization of HILs on T2-weighted sequences.